I don’t think the crashing will be a problem when the official version is released.
I wonder how many people will start using IE9 as their main browser – I think the IE usage will definitely increase once it’s been released. I hope Microsoft does updates and improves the HTML5 support, CSS3 selectors, etc.
IE9 isn’t supported by WinXP, which is kind of annoying.
I’m using Firefox4beta9 atm and I think it’s really cool.